MEGABLASTER2010 (2x100w TK2050)

[Saturnus]

No, none of them would be a good match IMO.

Get the PHT407 at Lautsprecher Intertechnik - Das Unternehmen - Lautsprecher für Selbstbau, Hifi, Pro Audio & Car Hifi

[Drakmin]

I found crossover design calculators, now I need to choose the crossover frequency. What do you recommend?

Precision Devices PDN.8BM31 AND P.Audio PHT407, would 3000hz 12db/okt be okay?

[Saturnus]

Originally Posted by Drakmin

I found crossover design calculators, now I need to choose the crossover frequency. What do you recommend?

Precision Devices PDN.8BM31 AND P.Audio PHT407, would 3000hz 12db/okt be okay?

Yeah, about that. Normally you'd chose x-over at about twice Fs, so 3KHz. In my Boominator mark II, I'm not pressing them very hard so even lower is ok (I use 2400 Hz).

[Drakmin]

Does this look okay crossover for ghettoblaster use? Is 5db okay dampening for tweeter? Btw. that http://www.intertechnik.de/ seemed pretty dead. I asked about postage cost for the tweeter via e-mail and got no answer.

http://www.p-audio.co.uk/products/db...23_pht-407.htm

http://www.precision-devices.com/asp...s/super/75.pdf

[Saturnus]

Look at the response graphs.

The woofer has a relatively flat response with 92 dB average sensitivity up to about 800 Hz where it rises dramatically with 3 dB. So your baseline sensitivity is 92 dB.

The tweeter has a slowly rising sensitivity down to 2KHz where it peaks with 101 dB. But is rather linear at 98 dB average from 3 Khz to about 13Khz (remember here that mp3s which is likely your most common source don't have information above 13KHz anyways).

With these points in mind you absolutely can't use a standard filter since you need the filter to cut both these peaks and still filter accurately. Now you can do that the easy way by adding bandstop filters, or the hard way by making educated guesses, and good old trial and error.

My starting point would be Butterworth filters since they are easier in the sense that you know the response is down 3 dB at the x-over frequency.

For the woofer I'd go with a 6 dB per octave filter at 1.5Khz because that will dampen the peak, and since we're not linearizing the impedance the filter effectiveness is dampened with rising frequency because of the rising impedance.

For the tweeter I'd go with a 12 dB per octave filter at 3KHz because that will dampen the tweeters peak and since again filter effeciency is decreased by rising impedance the actual x-over frequency should be around 2.5Khz.

Remember to attunate (dampen) the tweeter by 6 dB. Also please note that this will be a in-phase filter so you should not invert the tweeter.

Now I'd listen to it (and measure the response if you can) and slowly unwind the woofer filter coil until everything falls into to place but I'm pretty certain it won't require much tweaking as it's very similar to what I've done on the mark II version of my Boominator.

[Drakmin]

So cool you exist! Thanks!

[Drakmin]

I hope I understood all correctly. Are the drivers now in correct phase? I wasn't able to choose Butterworth for 6db slope, is this important. 6db slope calculator didn't have option for that.



To keep us entertained: (maybe add some hello kitty logos )

[Saturnus]

L-R and Butterworth are basically the same with 1st order filters, so yeah ... that's exactly what I would do.

Another alternative would be an L-pad that converts the impedance to 4 Ohms and change the tweeter filter to a 4 Ohms filter to avoid phase change at the x-over which would result in (if I recall correctly, others may correct me) 1.17 Ohm serial and 4.38 Ohms parallel.

[Saturnus]

Originally Posted by Saturnus

Another alternative would be an L-pad that converts the impedance to 4 Ohms and change the tweeter filter to a 4 Ohms filter to avoid phase change at the x-over which would result in (if I recall correctly, others may correct me) 1.17 Ohm serial and 4.38 Ohms parallel.

I must have had a bad-brain day yesterday.

To impedance correct with an L-pad you just parallel the tweeter with a 8 Ohm resitor between the L-pad and the tweeter. Now the L-pad will be Rs=2 and Rp=4 Ohms respectively.

Now since have 2 parallel resistors and we know the total impedance should be 2 Ohms for those 2 resistors and the tweeter itself, we can just reduce the 2 parallel resistors to one of 2.6667 Ohms.

To recap, to get the filter to see 4 Ohms impedance and have 6 dB dampening, Rs=2 and Rp=2.6667.

[Saturnus]

Originally Posted by Saturnus

I must have had a bad-brain day yesterday.

To impedance correct with an L-pad you just parallel the tweeter with a 8 Ohm resitor between the L-pad and the tweeter. Now the L-pad will be Rs=2 and Rp=4 Ohms respectively.

Now since have 2 parallel resistors and we know the total impedance should be 2 Ohms for those 2 resistors and the tweeter itself, we can just reduce the 2 parallel resistors to one of 2.6667 Ohms.

To recap, to get the filter to see 4 Ohms impedance and have 6 dB dampening, Rs=2 and Rp=2.6667.

EDIT (after timeout): It's pretty important that the values are correct in relation to eachother when impedance correcting, so I'd suggest 4 8 Ohms resistors paralleled for the serial one, and 3 8 Ohms resistors paralleled for the parallel one. Which also means you can use low wattage ones which are usually much higher quality.